1. Field of the Invention
The present invention relates to a device for generating an alarm signal in the event of a dangerous condition, e.g., fire, gas leakage, burglary, or the like.
2. Description of the Prior Art
Detectors, e.g., fire detectors, often generate an erroneous alarm due to smoke of, e.g., a cigarette, an electrical noise, and the like. In order to prevent this, as described in Japanese patent publication No. 45-35862, upon detection of a fire, the sensor is sometimes reset to allow its re-operation and, thereafter, is set to generate an alarm. A detector of this type, i.e., a so-called storage type fire receiver, has recently received a great deal of attention.
However, since the conventional storage type fire receiver judges an abnormality by detecting the repetitive ON/OFF operations of a switching element, e.g., an SCR, it cannot perform an actual storage operation, in which an abnormality is detected by monitoring that the density of, e.g., smoke caused by a fire has been at an operating level for a predetermined period of time. Therefore, the conventional fire receiver cannot reliably prevent erroneous generation of an alarm.